In every issue, we bring you the answers to real-world technical questions that have broad applications. Our technical support staff is available during normal business hours, Monday through Friday, by calling 800-321-8511 (Option 5)
We want to use machinable plastic rather than hard maple for the manufacture of metal spinning mandrels.
For that application, we would suggest Richlite, RenShape 5166, or RenShape 5179 as alternatives to the hard maple.
What is the difference between Thermoplastics and Thermoset materials?
Thermoplastics are materials that may be heated and formed and can be re-heated and returned to the liquid state.
Thermoset resins begin as a liquid polymers and are converted to solids during the molding process. This process is irreversible.
Does fiberglass have good chemical resistance?
Like glass, fiberglass fabrics are highly resistant to attack by most chemicals.
How thick must a PVA coat be to form a sufficient barrier? How do I know if PVA has been applied properly?
When applied correctly PVA should form a continuous film free of pinholes or air bubbles that is smooth and glossy when dry. Dry film thickness must be a least 2-4 mils (50-100 micron) on new/ reconditioned mold and at least 1-2 mils (25-50 micron) on seasoned mold. Two mils is approximately equal to the thickness of an industrial-type trash bag.
Each coat of PVA must be allowed to dry completely prior to applying additional coats or proceeding with molding. Keep in mind that entire coat, not just the surface, must dry completely in order to form an effective barrier. You may find it helpful to spray a test panel at the same time PVA is applied to mold in order to more easily check that coat has dried thoroughly.
We opened our can of Freeman Wax Release and it is watery. Is this normal? This is not normal. We believe elevated temperatures from the outside elements can cause the wax and mineral spirits to separate slightly causing the material to become watery.
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